One known type of plastic sprinkler includes a body and a rotatable sprinkler head which is rotated by the reaction force of water passing through the sprinkler head. In this form of sprinkler, at least one support arm projects upwardly from the body to provide a bearing above the sprinkler head, and the sprinkler head is rotatably mounted by the bearing and by another bearing within the body. Thus, the rotatable sprinkler head is rotatably mounted by the body and by the bearing which is external to the body.
As the sprinkler head rotates, it discharges water in a generally circular pattern. However, the support arm provides an obstruction in the circular pattern and interrupts the circular pattern. Accordingly, water is discharged in a generally circular segment which extends for less than 360 degrees. As a consequence, less than the full area which it is desired to irrigate receives water, and an excessive amount of irrigation water may drip from the support arm to a region adjacent the sprinkler.